Behavioral measures of olfactory discrimination in the rat will be used to measure the role played by those structures constituting the olfactory system. After assessing the role of several commissures and the effect of changing patterns of mucosal stimulation a "split-brain" preparation will be tested. Using a reversible nasal plug and artificial nasal septum transfer testing in the "split-brain" preparation will be conducted. Subsequently the effects upon olfactory discrimination of unilateral lesion in olfactory structures in "split- brain" animals will be determined. Here, performance of the animal using the lesioned side will be compared to performance using the unlesioned side. It is the goal of these experiments to define both the role of bilaterality and of individual structures in olfactory discrimination in the rat.